Sheaths for medical and dental probes are rapidly entering into frequent use to avoid contamination of such probes and cross infection of subsequent patients. For example, in Bala U.S. Pat. Nos. 4,823,949; 4,846,344; and 5,069,337, by way of example, inexpensive sheaths for oral thermometers, anal thermometers, and other probes are disclosed. These sheaths are made of heat-sealed sheets of plastic, packaged in an outer sheath which may have a paper side, with both the probe sheath and the outer package sheath being manufactured in a single sealing process.
There also is a need to provide inexpensive, disposable sheaths for various endoscopes, for example intraoral or dental cameras, as well as other endoscopes for penetration into the body interior through an anal route, an oral route, or the like. Such endoscopes have a distal end with an optical view opening which usually carries a lens, for viewing internal body areas from the endoscope proximal end.
It is highly desirable for the endoscope to be positioned in such a protective sheath with its lens or opening on the distal end facing an optically clear plastic sheet section of the sheath. However, the most desirable types of optically clear plastic film are somewhat tacky on their surface, so that if a sheath of such material is constructed, it can be difficult to insert the endoscope into the sheath. It should be remembered that, typically, a fairly tight fit is required between the endoscope and the sheath, particularly at the distal tip, where the sheath most desirably covers the lens in a tight manner so that folds or wrinkles of the sheath material are not found in front of the distal lens or opening of the endoscope.
Because of this, the best, optically clear plastic films have not been effectively useable in endoscope sheaths. Rather, less tacky plastic films have been used, which are less clear than the best, optically clear films, so that while the endoscope may be more easily inserted into the sheath, the image that the endoscope can project from its distal optical system to the user is less than optimum because of the reduced clarity of the sheath film material.
By this invention, a plastic film sheath for endoscopes is provided in which an optically clear plastic wall can be provided for the distal endoscope optics, but the sheath exhibits reduced frictional resistance to advancement of the endoscope into the sheath, for improved handling of the sheath and endoscope without any significant reduction in the quality of what is seen through the optical system thereof.